>>5d4140+Pb
These guys[1] hacked a NASA space probe and refired its motors. I read the entire blog once but I can't remember if there was any sort of encryption on the communication, although I know that was brought up. Modern probes do use cryptography, but I doubt Voyager does. I suspect if you fired commands at it you could control it. For the lulz or whatever.
[1] https://en.wikipedia.org/wiki/International_Cometary_Explore...